Effect of cycloheximide on the levels of nuclear HMG proteins in rat liver.

Within 30 minutes of administration of cycloheximide to rats, rRNA synthesis in isolated liver nuclei was inhibited by approximately 50%. The nuclear contents of high mobility group (HMG) proteins, including HMG 1, 2 and 14, were found to be decreased in parallel with the inhibition of RNA synthesis while the contents of the total cellular HMG proteins remained unchanged. The role of HMG proteins in the regulation of RNA synthesis is discussed.